The present invention relates to a video-based traffic surveillance system and more particularly to a system for surveilling a traffic strategic point such as an intersection, pedestrian crossing or the like by using a television (TV) camera.
FIG. 13 shows a conventional surveillance system which aims to surveille traffic at an intersection and its neighboring area by using a TV image. On the TV system in this figure are shown conditions of typical installation near an intersection of the surveillance system. On the other hand, FIG. 16 is a perspective view drawn from a photograph taken of an actual intersection and its neighboring area. Referring to the two figures, there are illustrated traffic signal lights proper 1, 1xe2x80x2N, traffic signal light posts 21, 2E, 2W, 2S and 2N (E, W, S and N represent directions, respectively), a housing 33 of a surveillance TV camera 3 as depicted in FIG. 14, and a post 4 of the surveillance TV camera 3. Denoted by 35 is a hold arm. The traffic signal lights are installed at east, west, south and north ends of the intersection in correspondence to passing directions of vehicles but for convenience of illustration, only bases of the posts 2E, 2W and 2S are depicted for the traffic signal lights at the east, west and south ends.
In FIG. 13, buildings near the intersection, passing vehicles and pedestrians are omitted for convenience of illustration, too, and arrows on the road surface do not imply traffic regulation but indicate passing directions of vehicles.
The surveillance TV camera 3 is constructed as shown in FIG. 14. More particularly, the TV camera proper 3 aiming at performing surveillance in all directions at the intersection is combined with a motor-driven zoom lens 31 to form a structure which is carried on a pan and tilt head 32. To permit surveillance in all kinds of weather, the structure is contained in the camera housing 33. Denoted by 34 is a carriage which is mounted to the hold arm 35 of the surveillance TV camera post 4.
The surveillance TV camera 3 is mounted at a position which is determined by taking into account such points that as shown in FIG. 16, drivers in passing vehicles do not have difficulties in visually recognizing the traffic signal light proper, the view field of the TV camera is not disturbed by a nearby traffic signal light and the TV camera is allowed to have an unobstructed distant view.
FIG. 15 shows a typical example of an image obtained from the surveillance TV camera (corresponding to an image from the TV camera 3 installed near the traffic signal light 1xe2x80x2N in FIG. 13). In this example, the direction of the TV camera is so adjusted that the confrontal traffic signal light 1S (not shown) can be viewed within the view field in order that the traffic flow near the intersection can be surveilled remotely. Further, when the image is recorded on a video tape recorder (VTR), not shown, the recorded image can be utilized to analyze causes of a traffic accident. But because of the aforementioned constraint imposed on the mount position, the TV camera is installed at only one corner, bringing about the following disadvantages.
(1) The pan and tilt head and the motor-driven zoom lens are used in combination to permit unobstructed views of all corners and as a result, the surveillance TV camera 3 and the housing 33 are increased in size. Accordingly, the surveillance TV camera post 4 needs to be highly rigid, leading to an increase in cost.
(2) In the example shown in FIG. 13 in which the TV camera 3 is installed at the north end of the intersection, a view field in the south direction can be ensured as shown in FIG. 15 but vehicles passing in the east and west directions are liable to be shaded by buildings and the traffic flow on this side lane. Especially, vehicles directly underneath and behind (northward) the surveillance TV camera 3 cannot at all be recognized.
(3) It fails to make traffic conditions in the all directions related to each other by having unobstructed views in the all directions at a time.
(4) When the TV camera manages to get a view of the confrontal traffic lights, it is difficult for the TV camera to ensure a view of an underneath area inside the intersection. If the traffic lights are viewed at an edge of the view field in order to get a wide view of the underneath area as illustrated in FIG. 13, the view field may sometimes deviate from the traffic lights in a heavily windy weather because both the camera and the traffic lights swing. Further, the view of the traffic lights is reduced in scale to make it difficult to discriminate colors.
In spite of the aforementioned disadvantages, the surveillance TV camera is installed at only one corner of the intersection. Presumably, this is because if TV cameras are installed at individual corners, the sidewalk will be jammed with not only illumination posts (not shown) and traffic signal light posts but also the surveillance TV camera posts and consequently the sidewalk area will be narrowed to disturb passage of pedestrians. In addition, the scenic beauty of city will be spoiled.
An example for elimination of the disadvantage in (2) above is available in which the surveillance camera post is installed closer to the intersection than the traffic signal light post and the arm 35 is extended up to the center of the intersection as shown in FIG. 16. In this instance, however, the disadvantages in (1) and (4) above are conversely aggravated. In the example shown in FIG. 16, a structure is employed which permits a person to easily access the TV camera for the purpose of maintenance and in that case, both the post and the arm are required to be high in strength and are necessarily increased in size.
When an image of the surveillance TV camera is desired to be used, for multi-purpose, as a part of an advanced traffic control system, conditions of traffic flow in all directions at an intersection and its neighboring area must be grasped simultaneously from an optimal position. To this end, one solution is to install surveillance TV cameras at the individual corners. But if this is realized by installing the traffic signal light and the surveillance TV camera independently of each other as in the case of the prior art, disadvantages of the disturbance of passage of pedestrians and the spoilage of the scenic beauty of city will be actualized. Therefore, a method for camera installation which can eliminate these disadvantages is desired.
Conventionally, another system is available which automatically measures speed violation but as far as violation of traffic lights is concerned, the arrest of a flagrant offender by visual inspection prevails predominantly. In the arrest of a flagrant offender by visual inspection, it is necessary for a person who exposes a violator to always surveille the appearance of a violative vehicle by repeating such an operation as watching a light indication of a traffic signal light and then watching a predictive area in which the violative vehicle will appear. As will be seen from the above, the conventional system raises problems that the arrest of a violative vehicle is carried out by having resort to manual inspection to increase personnel expenses, all traffic signal lights cannot be surveilled, no evidence for traffic light violation is left behind, judgement during transition of a change of the traffic light tends to be obscure and determination of a violation area becomes obscure, thus making a judgement miss liable to occur. Further, in the conventional system in which the traffic signal light and the surveillance TV camera are installed independently of each other, the total of costs of installation of equipments tends to be comparatively high and traffic regulations practiced during installation work and maintenance/inspection have a great influence upon traffic.
The present invention contemplates elimination of the conventional problems as above and it is an object of the present invention to provide a traffic strategic point surveillance system based on a TV camera which can also be applicable to an advanced traffic control system.
The advanced traffic control system referred to herein is a system which using an image of a surveillance TV camera in combination with image processing techniques, optimize traffic signal lights control by automatic detection of passing vehicle speed, vehicle congestion, avoide the obstacles, length of traffic jam, and travel time measuring by license plate recognition, and prevent a traffic accident occurring by automatic detection of illegal parking vehicles.
Another object of the present invention is to provide a surveillance TV system capable of obtaining an image of high utilization value which is also utilizable in the advanced traffic control system by fetching information of traffic lights at individual corners into images of individual surveillance TV cameras.
When the traffic lights and the surveillance TV camera are installed close to each other or contained in the same housing so that a lighting color of the traffic lights may be superimposed on an image of the surveillance TV camera every moment so as to be displayed at a corner of the image, running conditions of vehicles in each direction can be analyzed every moment in association with the state of the traffic lights. Further, the surveillance TV camera need not catch the confrontal traffic lights in its view field, because, unlike prior art Surveillance TV camera which is required to be so set as to allow the confrontal traffic lights to be caught in its view field as shown in FIG. 15, the confrontal traffic lights are picked up by another means in the present invention and the traffic lights thus picked up are superimposed on an image being taken by the surveillance TV camera and the colors of the traffic lights are displayed at a corner portion of the image, whereby the degree of freedom of view-field adjustment can be increased, so that a view field inside the intersection which is important for analysis of a traffic accident can especially be ensured, thus providing an image of traffic flow of high utilization value.
Preferably, in the present invention, by using a TV camera, a video recording unit such as a VTR and image processing techniques, an image of a traffic light violative (light neglecting) car and the traffic lights may be recorded simultaneously and automatically in synchronism with a change in the traffic lights with the aim of efficiently proving traffic light violation.
As necessary, in the present invention, installation of surveillance TV cameras at the individual corners can be realized to solve the conventional problems described previously by making the traffic lights integral with each surveillance TV camera to permit a single post to be used in common for the traffic light post and the surveillance TV camera post.
When the surveillance TV cameras are installed at the individual corners of an intersection and video outputs of the cameras are displayed on individual TV monitors arranged on a display board of a traffic control center, intuitional grasp of actual traffic conditions at the intersection is difficult to achieve depending on the relation between a screen displayed on the monitor and a direction in which the TV camera is image-picking up. For example, when the screen displayed on the monitor is inverse to or 90xc2x0 differs from the direction of image-picking up by the TV camera on the display board, the direction must be displaced for consideration in order to concretely grasp conditions of the intersection, giving rise to very troublesome work. Accordingly, in the traffic control center, it is difficult for persons concerned, except experts, to intuitionally grasp the state of traffic flow passing through the intersection from such a map type (geographic) display board as above.
The present invention also intends to eliminate the above disadvantage and still another object of the present invention is to provide a surveillance TV system in which directions of images of the respective TV cameras displayed on the respective TV monitors coincident with directions on the map regardless of surveillance directions of the respective TV cameras to enable even an inexperienced person to intuitionally grasp the traffic flow. In other words, in the present invention, directions on the screen display are made to coincide with directions on the map.
For example, according to the present invention, in a TV system which comprises a plurality of TV cameras and a plurality of TV monitors to surveille and record the traffic flow by displaying images of a traffic strategic point such as an intersection on the TV monitors at a time, the plurality of TV cameras for image-picking up the intersection preferably image-pick up an area inside the intersection and roads extending forwards from the intersection to prevent the dead angle from occurring and images of the respective TV cameras are displayed on the respective TV monitors in such a manner that directions of the displayed images of the respective TV cameras are made to coincide with directions on the map type information board regardless of the surveillance directions of the respective TV cameras.
Further, according to the present invention, in a TV system which comprises a plurality of TV cameras and a plurality of TV monitors to surveille and record the traffic flow by displaying images of a traffic strategic point such as an intersection at a time, one of the TV cameras for image-picking up an area in a first direction of the intersection preferably has a longitudinally elongated screen and an area inside the intersection and a road ahead of the intersection are picked up by this TV camera in a manner which provides no dead angle. Another TV camera has its share of the image-picking up range for image-picking up a road ahead of the intersection in a second direction orthogonal to the first direction. Further, images of the respective TV cameras displayed on the respective TV monitors are preferably arranged on a single screen in such a manner that directions of the images coincide with directions on a map of the map type information board regardless of surveillance directions of the respective TV cameras, with the result that the image of the respective road portions picked up by the respective TV cameras have images sizes which approximate with respect to each other on the single screen.
When the image of the surveillance TV camera is utilized, for multi-purpose, as a part of the advanced traffic control system, it is more desirable to have a bird-eye""s view of traffic flow conditions in all directions at the neighboring area of an intersection. In the aforementioned system of the present invention in which the traffic signal lights and the surveillance TV cameras are installed independently for each direction, however, the degree of improvements in elimination of the disturbance of passage of pedestrians and the spoilage of the scenic beauty of city is limited.
Accordingly, still another object of the present invention is to provide a surveillance TV system capable of obtaining an image of higher utilization value which can also be utilized in the advanced traffic control system by taking bird-eye""s views in all directions at the intersection at a time and fetching information of traffic lights into one surveillance TV camera.
By displaying a lighting color of traffic lights together with an image of the surveillance TV camera in accordance with the traffic flow every moment, running conditions of vehicles can be analyzed in association with the state of the traffic lights. Further, when the surveillance TV camera need not catch the confrontal traffic lights in its view field, the degree of freedom of view field adjustment is increased and a view of the entire area inside the intersection, which is important especially for analysis of a traffic accident, can be ensured, thus providing an image of traffic flow which is of high utilization value.